Infection in the udder is a major problem in dairy cows. It is caused by bacteria which in most cases enters the udder through the teat orifice.
It is the teat orifice or the streak canal that forms a primary defense mechanism to invading micro-organisms. Deposits of keratin sit in the streak canal (sometimes known as the teat end canal) to form a natural defensive plug. Keratin contains high levels of naturally occurring antibacterial substances which inhibit the passage of bacteria. The keratin deposits are more dense in dry cows than lactating cows. The reason for this is that during the dry period, keratin forms a solid plug which protects the teat from invading bacteria.
Sometimes dry period sub clinical mastitis infections will occur and these can be carried on to manifest themselves as clinical mastitis at calving or during the next lactation. Streptococcus uberis is a type of bacteria that commonly infects dry udders and appears as clinical mastitis at calving time.
Some types of treatments are administered at drying off to cure sub-clinical infections or as a preventative treatment designed to protect the udder from new infections during the high-risk dry period, especially immediately after drying off. Dry period therapy often consists of antibiotics which are in a sustained release base to provide prolonged antibacterial protection during the early dry period when the streak canal keratin is forming a natural seal or barrier against such infection risks.
Once the streak canal seal is in place, the risk of infections is lower. However, there is a tendency for new infections to occur during the immediate post-drying off period if cows are not treated with a protective dry period antibiotic. This is more likely to occur when teat end damage or trauma has occurred that can delay or disrupt the formation of the streak canal seal.
Additionally, the build up of milk pressure immediately following the cessation of regular milking at drying off may cause milk to leak from the teats, disrupting keratin formation and increasing the risk of infection.
Treatments for dry period therapy are often administered as infusions of antibiotics by a plastic needle or nozzle placed into the teat orifice and into the streak canal or teat cistern (papillary sinus).
One example of this is U.S. Pat. No. 4,472,374 which discloses an intramammary composition containing a siloxane elastomer incorporating an antibacterial agent.
In order to facilitate application to the teat, U.S. Pat. No. 4,472,374 requires that “the elastomer must be of sufficiently low viscosity to facilitate the application to the mammary glands by injection via the streak canal and teat cistern”. U.S. Pat. No. 4,472,374 further teaches that the elastomer must remain sufficiently elastic to remain in place and soft enough to be milked-out at the onset of lactation. As such, an inert fluid silicone may be used to obtain “a liquid elastomer of the desired properties”.
Best results were obtained in U.S. Pat. No. 4,472,374 when the majority of the elastomer was infused into the teat sinus, and the remainder of the elastomer was discharged into the streak canal as the infusion means/applicator was withdrawn out of the teat.
U.S. Pat. No. 4,472,374 however suffers from a number of disadvantages. In order for the low viscosity composition to be retained within the udder during the dry period, the majority of the compositions must be infused into the teat sinus, where the antibacterial agents are diluted and of less use in preventing mastitis and may also cause additional problems such as irritations and residues.
The low viscosity composition of U.S. Pat. No. 4,472,374 also has no defined form, and thus does not permit any control to be exercised over the placement, size or shape of the elastomer infused into the streak canal. Accordingly, it is not possible for a user to control the placement or volume of elastomer infused into the streak canal and thus it is also not possible to control the dose of antibacterial agent delivered.
Further, due to the low viscosity of the composition, it is difficult to ensure complete removal before lactation commences.
Lactating animals used for milk production are exposed to mechanical milking machines, normally twice a day. These machines apply vacuum pulsation to the teat for milking purposes.
Understandably, mechanical milking can cause damage to the teat end. High vacuum, faulty pulsation and over-milking can bruise tissue and erode the teat end—breaking down the natural defenses of the teat. This can occur from infected teat lesions forming, damaged tissue and a loss of teat end integrity allowing bacteria to enter the udder. These will also influence dry period new infections with the inability of the teat to form an effective keratin shield over the dry period.
In some situations, surgical procedures may be used to repair damaged teats. After surgery, an intramammary antibiotic is infused into the teat cistern to prevent and/or treat mastitis, before a teat insert or sterile silicone implant is inserted into the teat canal to prevent the narrowing or collapse of the teat canal after surgery. However, these inserts are designed to provide temporary support for the teat canal of damaged teats only and do not themselves contain any medicament.
Mastitis occurs in various forms depending on the type of micro-organism causing the infection. It causes lost milk production, and adversely affects the flow and quality of milk. During lactation, mastitis can occur as clinical mastitis, which is visually recognising and treatable. Clinical mastitis is treated during lactation using a multiple number of antibiotic infusions at milking time. Care must be taken to avoid contaminating the milk supply with antibiotic residues.
The economic significance of mastitis is considerable. The common way to treat mastitis is with intramammary antibiotics infused into the udder through the teat orifice and via the streak canal. The antibiotic is absorbed into the alveolus in secretary tissue where the infection normally resides. These antibiotics come in various formulations but usually consist of an antibiotic formulated in paste or oil base which is infused by inserting a plastic tip through the orifice and squeezing the antibiotic from the tube into the udder.
The antibiotic is infused after milking. Since the cow must be milked regularly to maintain lactation and also to avoid discomfort, the cow is milked at the next milking period, removing much of the antibiotic treatment. Consequently, repeated treatments are infused to maintain adequate drug levels. This milk must be discarded as it is contaminated with inhibitory substances.
Other problems associated with the present treatment of mastitis include:                Treatment of cows at drying off as a preventative procedure requires an antibiotic which can remain in the udder for 20 days over the cow's dry period. The antibiotic must have an active duration which does not contaminate the milk of fresh calved cows with antibiotic residues in the immediate post-calving period. In particular, antibacterial activity is important over the first ten days of drying off.        Treatment of clinical mastitis during lactation requires the infusion of one to three successive antibiotics into a lactating udder. Consequently, the cow must be milked each day with the treatment period being up to three days. Therefore when the antibiotic is infused, the main bulk of the antibiotic is removed from the udder when the cow is milked at the next milking, requiring a further treatment after the milking to restore the required level of antibiotic to treat the infection.         The wastage of antibiotic in the removed milk and constant administration of a further treatment is costly. There is also potential risk from the farmer inadvertently allowing the milk to go to the bulk tank. This can lead to the farmer incurring severe antibiotic residue penalties.        
All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of the documents form part of the common general knowledge in the art, in New Zealand or in any other country.
It is acknowledged that the term ‘comprise’ may, under varying jurisdictions, be attributed with either an exclusive or an inclusive meaning. For the purpose of this specification, and unless otherwise noted, the term ‘comprise’ shall have an inclusive meaning—ie that it will be taken to mean an inclusion of not only the listed components it directly references, but also other non-specified components or elements. This rationale will also be used when the term ‘comprised’ or ‘comprising’ is used in relation to one or more steps in a method or process.
It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice.
Further aspects and advantages of the present invention will now be described by way of example only.